A welding state detecting and recording device is known to the art. The known device is provided with a toroidal coil for detecting indices relating to welding current of a resistance-welding machine, and a data storing means for storing data based on the indices detected by the toroidal coil. The toroidal coil and the data storing means are connected by a long cable (first prior art).
Further, Japanese Laid Open Patent Publication (TOKKAIHEI) 8-99181 discloses a welding state detecting and transmitting device. The device is utilized after being attached to a secondary side of a resistance-welding machine. The welding state detecting and transmitting device is provided with a toroidal coil for detecting welding current indices of the resistance-welding machine, and a transmitting means for wirelessly transmitting data based on the indices detected by the toroidal coil to an external device for processing received data (second prior art).
In the case of the first prior art, the toroidal coil must be attached to a welding gun (a secondary side) of the resistance-welding machine. The welding gun is moved in accordance with a welding point within a work to be welded. Attaching the toroidal coil, being connected to the cable, to the movable welding gun often causes a problem that, as the welding gun is moved around the work, the long cable connected to the toroidal coil is to catch on or become entangled with the work or the other members. This causes the cable to be severed, or damaging the work or the other members. Further, it is even more likely that the cable will catch on or become entangled with the work when the welding gun is caused to move sequentially around the work so as to weld a plurality of points. Therefore, it is difficult to adopt the first prior art in an industrial application.
The device of the second prior art wirelessly transmits the data to the external device, thereby resolving the problem in the first prior art that may be caused by the long cable between the toroidal coil and the data recording means.